Interface localization in thin ferromagnetic films

Interface localization in a thin ferromagnetic film with competing surface fields has been investigated by Monte Carlo simulation for an anisotropic Heisenberg model as a function of temperature and the anisotropy of the exchange interaction Lambda. In the isotropic model limit, where Lambda --> 0, no spontaneous magnetization of the film is observed and the magnetization profile across the film is antisymmetric, slowly varying from positive magnetization on one surface to negative on the other. However, in the limit Lambda --> 1, when the model Hamiltonian is equivalent to that of the Ising model, a non-zero magnetization of the film is observed below a critical temperature T-c. This is associated with a localization of the interface between regions of positive and negative magnetization near the film surface and a degeneracy in the magnetization profiles exists between states of positive and negative total magnetization at low temperatures. The results of magnetic relaxation studies indicate that the magnetization decays exponentially with a relaxation time that increases with Lambda and decreases with temperature.